draft-ietf-spring-sr-replication-segment-00.txt   draft-ietf-spring-sr-replication-segment-01.txt 
Network Working Group D. Voyer, Ed. Network Working Group D. Voyer, Ed.
Internet-Draft Bell Canada Internet-Draft Bell Canada
Intended status: Standards Track C. Filsfils Intended status: Standards Track C. Filsfils
Expires: January 27, 2021 R. Parekh Expires: May 1, 2021 R. Parekh
Cisco Systems, Inc. Cisco Systems, Inc.
H. Bidgoli H. Bidgoli
Nokia Nokia
Z. Zhang Z. Zhang
Juniper Networks Juniper Networks
July 26, 2020 October 28, 2020
SR Replication Segment for Multi-point Service Delivery SR Replication Segment for Multi-point Service Delivery
draft-ietf-spring-sr-replication-segment-00 draft-ietf-spring-sr-replication-segment-01
Abstract Abstract
This document describes the SR Replication segment for Multi-point This document describes the SR Replication segment for Multi-point
service delivery. A SR Replication segment allows a packet to be service delivery. A SR Replication segment allows a packet to be
replicated from a replication node to downstream nodes. replicated from a replication node to downstream nodes.
Requirements Language Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
skipping to change at page 1, line 44 skipping to change at page 1, line 44
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
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This Internet-Draft will expire on January 27, 2021. This Internet-Draft will expire on May 1, 2021.
Copyright Notice Copyright Notice
Copyright (c) 2020 IETF Trust and the persons identified as the Copyright (c) 2020 IETF Trust and the persons identified as the
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Replication Segment . . . . . . . . . . . . . . . . . . . . . 3 2. Replication Segment . . . . . . . . . . . . . . . . . . . . . 3
3. Use Cases . . . . . . . . . . . . . . . . . . . . . . . . . . 4 2.1. SRv6 . . . . . . . . . . . . . . . . . . . . . . . . . . 4
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5 2.1.1. End.Replicate: Replicate and/or Decapsulate . . . . . 6
5. Security Considerations . . . . . . . . . . . . . . . . . . . 5 2.1.2. H.Encaps.Replicate: SR Headend encapsulation in
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5 Replication Segment . . . . . . . . . . . . . . . . . 7
7. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 5 3. Use Cases . . . . . . . . . . . . . . . . . . . . . . . . . . 7
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 6 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
8.1. Normative References . . . . . . . . . . . . . . . . . . 6 5. Security Considerations . . . . . . . . . . . . . . . . . . . 8
8.2. Informative References . . . . . . . . . . . . . . . . . 7 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 8
Appendix A. Illustration of a Replication Segment . . . . . . . 7 7. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 10
8.1. Normative References . . . . . . . . . . . . . . . . . . 10
8.2. Informative References . . . . . . . . . . . . . . . . . 10
Appendix A. Illustration of a Replication Segment . . . . . . . 11
A.1. SR-MPLS . . . . . . . . . . . . . . . . . . . . . . . . . 11
A.2. SRv6 . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 15
1. Introduction 1. Introduction
We define a new type of segment for Segment Routing [RFC8402], called We define a new type of segment for Segment Routing [RFC8402], called
Replication segment, which allows a node (henceforth called as Replication segment, which allows a node (henceforth called as
Replication Node) to replicate packets to a set of other nodes Replication Node) to replicate packets to a set of other nodes
(called Downstream Nodes) in a Segment Routing Domain. Replication (called Downstream Nodes) in a Segment Routing Domain. Replication
segments provide building blocks for Point-to-Multipoint Service segments provide building blocks for Point-to-Multipoint Service
delivery via SR Point-to-Multipoint (SR P2MP) policy. A Replication delivery via SR Point-to-Multipoint (SR P2MP) policy. A Replication
segment can replicate packet to directly connected nodes or to segment can replicate packet to directly connected nodes or to
downstream nodes (without need for state on the transit routers). downstream nodes (without need for state on the transit routers).
This document focuses on the Replication Segment building block. The Replication segments apply equally to both SR-MPLS and SRv6
use of one or more stitched Replication Segments constructed for SR instantiations of Segment Routing. This document focuses on the
P2MP Policy tree is specified in [I-D.voyer-pim-sr-p2mp-policy]. Replication Segment building block. The use of one or more stitched
Replication Segments constructed for SR P2MP Policy tree is specified
in [I-D.ietf-pim-sr-p2mp-policy].
2. Replication Segment 2. Replication Segment
In a Segment Routing Domain, a Replication segment is a logical In a Segment Routing Domain, a Replication segment is a logical
construct which connects a Replication Node to a set of Downstream construct which connects a Replication Node to a set of Downstream
Nodes. A Replication segment is a local segment instantiated at a Nodes. A Replication segment is a local segment instantiated at a
Replication node. It can be either provisioned locally on a node or Replication node. It can be either provisioned locally on a node or
programmed by a PCE. Replication segments apply equally to both SR- programmed by a PCE.
MPLS and SRv6 instantiations of Segment Routing.
A Replication segment is identified by the tuple <Replication-ID, A Replication segment is identified by the tuple <Replication-ID,
Node-ID>, where: Node-ID>, where:
o Replication-ID: An identifier for a Replication segment that is o Replication-ID: An identifier for a Replication segment that is
unique in context of the Replication Node. unique in context of the Replication Node.
o Node-ID: The address of the Replication Node that the Replication o Node-ID: The address of the Replication Node that the Replication
segment is for. Note that the root of a multi-point service is segment is for. Note that the root of a multi-point service is
also a replication node. also a replication node.
In simplest case, Replication-ID can be a 32-bit number, but it can In simplest case, Replication-ID can be a 32-bit number, but it can
be extended or modified as required based on specific use of a be extended or modified as required based on specific use of a
Replication segment. When the PCE signals a Replication segment to Replication segment. When the PCE signals a Replication segment to
its node, the <Replication-ID, Node-ID> tuple identifies the segment. its node, the <Replication-ID, Node-ID> tuple identifies the segment.
Examples of such signaling and extension are described in Examples of such signaling and extension are described in
[I-D.voyer-pim-sr-p2mp-policy]. [I-D.ietf-pim-sr-p2mp-policy].
A Replication segment includes the following elements: A Replication segment includes the following elements:
o Replication SID: The Segment Identifier of a Replication segment. o Replication SID: The Segment Identifier of a Replication segment.
This is a SR-MPLS label or a SRv6 SID [RFC8402]. This is a SR-MPLS label or a SRv6 SID [RFC8402].
o Downstream Nodes: Set of nodes in Segment Routing domain to which o Downstream Nodes: Set of nodes in Segment Routing domain to which
a packet is replicated by the Replication segment. a packet is replicated by the Replication segment.
o Replication State: See below. o Replication State: See below.
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plane. At a Replication node, the Replication SID is the equivalent plane. At a Replication node, the Replication SID is the equivalent
of Binding SID [I-D.ietf-spring-segment-routing-policy] of a Segment of Binding SID [I-D.ietf-spring-segment-routing-policy] of a Segment
Routing Policy. Routing Policy.
A packet steered into a Replication segment at a Replication node is A packet steered into a Replication segment at a Replication node is
replicated to each Downstream Node with the Downstream Replication replicated to each Downstream Node with the Downstream Replication
SID that is relevant at that node. A packet is steered into a SID that is relevant at that node. A packet is steered into a
Replication Segment in two ways: Replication Segment in two ways:
o When the Active Segment [RFC8402] is the Replication SID. In this o When the Active Segment [RFC8402] is the Replication SID. In this
case, the operation for a replicated copy is CONTINUE. case, the operation is NEXT followed by a PUSH for a replicated
copy.
o On the root of a multi-point service, based on local policy-based o On the root of a multi-point service, based on local policy-based
routing. In this case, the operation for a replicated copy is routing. In this case, the operation for a replicated copy is
PUSH. PUSH.
If a Downstream Node is an egress (aka leaf) of the multi-point If a Downstream Node is an egress (aka leaf) of the multi-point
service, i.e. no further replication is needed, then that leaf node's service, i.e. no further replication is needed, then that leaf node's
Replication segment will not have any Replication State and the Replication segment will not have any Replication State and the
operation is NEXT. At an egress node, the Replication SID MAY be operation is NEXT. At an egress node, the Replication SID MAY be
used to identify that portion of the multi-point service. Notice used to identify that portion of the multi-point service. Notice
that the segment on the leaf node is still referred to as a that the segment on the leaf node is still referred to as a
Replication segment for the purpose of generalization. Replication segment for the purpose of generalization.
A node can be a bud node, i.e. it is a replication node and a leaf A node can be a bud node, i.e. it is a replication node and a leaf
node of a multi-point service at the same time node of a multi-point service at the same time
[I-D.voyer-pim-sr-p2mp-policy]. In this case, the Replication [I-D.ietf-pim-sr-p2mp-policy]. In this case, the Replication
segment's Replication State includes a branch with the Downstream segment's Replication State includes a branch with the Downstream
Node being itself and the operation for the replicated copy is NEXT. Node being itself and the operation for the replicated copy is NEXT.
The Replication SID MUST be the last SID (at the bottom of stack for The Replication SID MUST be the last SID (at the bottom of stack for
SR-MPLS) in a packet that is steered out from a Replication node of a SR-MPLS) in a packet that is steered out from a Replication node of a
Replication Segment. The behavior at Downstream nodes of a Replication Segment. The behavior at Downstream nodes of a
Replication Segment is undefined If there are any SIDs after the Replication Segment is undefined If there are any SIDs after the
Replication SID and is outside the scope of this document. Replication SID and is outside the scope of this document.
2.1. SRv6
SRv6 network programming [I-D.ietf-spring-srv6-network-programming]
introduces concept of functions. A function defines local behavior
on a node and is identified by opaque function part of a SRv6 SID.
Familiarity with SRv6 Network Programming is expected.
In SRv6, a Replication Segment can be realized by defining a SRv6
Segment Endpoint behavior for replication. End.Replicate is an
Endpoint function for replicating packets and, if required,
decapsulation and processing of next header. This function is bound
to a local SRv6 Replication SID at the Replication Node and
Downstream Nodes of a Replication segment. FUNCT part of a
Replication SID can represent both replication function as well the
Replication State of a specific Replication Segment, or the
Replication state MAY be represented by ARG part of Replication SID.
For example, assuming two Replication Segments, RS1 and RS2 at a
node, the node can bind two functions 0x00F1 and 0x00F2 (F=16, A=0)
to End.Replicate function on Replication Segments RS1 and RS2
respectively. The node can also choose to bind one function 0x00FA
with End.Replicate and ARGs 0x0001 and 0x0002 (F=16, A=16) to RS1 and
RS2 respectively.
A Replication Node will replicate packet matching local SRv6
Replication SID to all Downstream Nodes. Each replication is
equivalent to pushing segment list of an SRv6 policy to a Downstream
Node, If there is only one SID, the Downstream Replication SID and
there is no need to use any Flag, Tag or TLV, the SRH MAY be omitted
and the Downstream Replication SID is set as IPv6 DA in replicated
copy of packet. In this case, the LOC part of routed Downstream
Replication SID takes packet from Replication Node to the Downstream
Node. If an SRH is inserted in a replicated copy of packet, the
Downstream Replication SID MUST be the last Segment in SRH i.e at
Segment List index 0.
If a Downstream Node is an egress (aka leaf) of the multi-point
service, i.e. no further replication is needed, then that leaf node's
Replication segment will not have any Replication State and the
operation on packet wtih local Replication SID is decapsulation with
processing of next header equivalent to End.DT46.
A bud node performs both the replication and decapsulation part of
End.Replicate function on a packet with local Replication SID.
H.Encaps.Replicate is behavior on the root of a multipoint service to
steer a packet into a SRv6 Replication Segment.
Considerations of SRv6 Small SID/Compresion SID for SRv6 Replication
SID will be addressed in future revision of this document.
2.1.1. End.Replicate: Replicate and/or Decapsulate
The "Endpoint with replication and/or decapsulate behavior
(End.Replicate for short) is variant of End behavior.
We define a generic Replicate function on a packet for Replication
State (RS).
S01. Replicate(RS, packet)
S02. {
S03. For each Replication R with Downstream Replication SID, R-SID {
S04. Make copy of packet
S05. If (NumSID(R)== 1) {
S06. Set IPv6 DA = R-SID
S07. Set NH-Header in copy to Next-Header value of packet
S08. } Else {
S09. Insert SRH with R-SID at SID List[0] followed by other SIDS
S10. Set NH-Header of SRH to Next-Header value of packet
S10. Set IPv6 DA = First SID of R
S11. Set NH-Header in copy to SRH
S12. }
S13. Submit the packet to the egress IPv6 FIB lookup and
transmission to the new destination
S14. }
When N receives a packet whose IPv6 DA is S and S is a local
End.Replicate SID, N does:
S01. Lookup FUNCT OR (FUNCT,ARG) portion of S to get Replication State RS
S02. Call Replicate(RS, packet)
S03. If NH==SRH and SL != 0 {
S04. Send an ICMP Parameter Problem to the Source Address,
Code 0 (Erroneous header field encountered),
Pointer set to the Segments Left field,
interrupt packet processing and discard the packet.
S05. } Else If "decap check" success: {
S06. Process packet according to End.DT46 behavior in SRv6 Network Programming
S07. } Else {
S08. Drop packet
S09. }
Notes:
The "decap check" would succeed on egress or bud node. The SRv6
Replication SID is bound to a specific tenant table at these nodes.
2.1.2. H.Encaps.Replicate: SR Headend encapsulation in Replication
Segment
Node N receives two packets P1=(A, B2) and P2=(A,B2)(B3, B2, B1;
SL=1). B2 is neither a local address nor SID of N.
Node N is configured with an IPv6 Address T (e.g. assigned to its
loopback).
N steers the transit packets P1 and P2 into an SRv6 Replication
Segment, R, with a Source Address T and Replication State RS..
The H.Encaps.Replicate encapsulation behavior is defined as follows:
S01. Push an IPv6 header
S02. Set outer IPv6 SA = T
S03. Set outer Payload Length, Traffic Class, Hop Limit and
Flow Label fields
S04. Set the outer Next-Header value
S05. Decrement inner IPv6 Hop Limit or IPv4 TTL
S06. Call Replicate(RS, Outer packet)
After the H.Encaps behavior, assuming a directly adjacent Downstream
Node with Downstream Replication SID, D-RSID, P1' and P2'
respectively look like:
- (T, D-RSID) (A, B2)
- (T, D-RSID) (A, B2) (B3, B2, B1; SL=1)
After the H.Encaps behavior, assuming a non-adjacent Downstream Node
with Downstream Replication SID, D-RSID and a Segment list <S1, S2>
to reach Downstream Node, P1' and P2' respectively look like:
- (T, S1) (D-RSID, S2, S1; SL=2) (A, B2)
- (T, S1) (D-RSID, S2, S1; SL=2) (A, B2) (B3, B2, B1; SL=1)
3. Use Cases 3. Use Cases
In the simplest use case, a single Replication segment includes the In the simplest use case, a single Replication segment includes the
root node of a multi-point service and the egress/leaf nodes of the root node of a multi-point service and the egress/leaf nodes of the
the service as all the Downstream Nodes. This achieves Ingress the service as all the Downstream Nodes. This achieves Ingress
Replication [RFC7988] that has been widely used for MVPN [RFC6513] Replication [RFC7988] that has been widely used for MVPN [RFC6513]
and EVPN [RFC7432] BUM (Broadcast, Unknown and Multicast) traffic. and EVPN [RFC7432] BUM (Broadcast, Unknown and Multicast) traffic.
Replication segments can also be used as building blocks for Replication segments can also be used as building blocks for
replication trees when Replication segments on the root, intermediate replication trees when Replication segments on the root, intermediate
replication nodes and leaf nodes are stitched together to achieve replication nodes and leaf nodes are stitched together to achieve
efficient replication. That is specified in efficient replication. That is specified in
[I-D.voyer-pim-sr-p2mp-policy]. [I-D.ietf-pim-sr-p2mp-policy].
4. IANA Considerations 4. IANA Considerations
This document makes no request of IANA. This document requires registration of End.Replicate behavior in
"SRv6 Endpoint Behaviors" sub-registry of "Segment Routing
Parameters" top-level registry.
+-------+-----+------------------------+-----------+
| Value | Hex | Endpoint behavior | Reference |
+-------+-----+------------------------+-----------+
| TBD | TBD | End.Replicate | [This.ID] |
| TBD | TBD | End.Replicate with ARG | [This.ID] |
+-------+-----+------------------------+-----------+
Table 1: IETF - SRv6 Endpoint Behaviors
5. Security Considerations 5. Security Considerations
There are no additional security risks introduced by this design. There are no additional security risks introduced by this design.
6. Acknowledgements 6. Acknowledgements
The authors would like to acknowledge Siva Sivabalan, Mike Koldychev, The authors would like to acknowledge Siva Sivabalan, Mike Koldychev,
Vishnu Pavan Beeram, Alexander Vainshtein, Bruno Decraene and Joel Vishnu Pavan Beeram, Alexander Vainshtein, Bruno Decraene and Joel
Halpern for their valuable inputs. Halpern for their valuable inputs.
skipping to change at page 6, line 48 skipping to change at page 10, line 15
8. References 8. References
8.1. Normative References 8.1. Normative References
[I-D.ietf-spring-segment-routing-policy] [I-D.ietf-spring-segment-routing-policy]
Filsfils, C., Talaulikar, K., Voyer, D., Bogdanov, A., and Filsfils, C., Talaulikar, K., Voyer, D., Bogdanov, A., and
P. Mattes, "Segment Routing Policy Architecture", draft- P. Mattes, "Segment Routing Policy Architecture", draft-
ietf-spring-segment-routing-policy-08 (work in progress), ietf-spring-segment-routing-policy-08 (work in progress),
July 2020. July 2020.
[I-D.ietf-spring-srv6-network-programming]
Filsfils, C., Camarillo, P., Leddy, J., Voyer, D.,
Matsushima, S., and Z. Li, "SRv6 Network Programming",
draft-ietf-spring-srv6-network-programming-24 (work in
progress), October 2020.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>. <https://www.rfc-editor.org/info/rfc2119>.
[RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L., [RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L.,
Decraene, B., Litkowski, S., and R. Shakir, "Segment Decraene, B., Litkowski, S., and R. Shakir, "Segment
Routing Architecture", RFC 8402, DOI 10.17487/RFC8402, Routing Architecture", RFC 8402, DOI 10.17487/RFC8402,
July 2018, <https://www.rfc-editor.org/info/rfc8402>. July 2018, <https://www.rfc-editor.org/info/rfc8402>.
8.2. Informative References 8.2. Informative References
[I-D.voyer-pim-sr-p2mp-policy] [I-D.filsfils-spring-srv6-net-pgm-illustration]
Filsfils, C., Camarillo, P., Li, Z., Matsushima, S.,
Decraene, B., Steinberg, D., Lebrun, D., Raszuk, R., and
J. Leddy, "Illustrations for SRv6 Network Programming",
draft-filsfils-spring-srv6-net-pgm-illustration-03 (work
in progress), September 2020.
[I-D.ietf-pim-sr-p2mp-policy]
Voyer, D., Filsfils, C., Parekh, R., Bidgoli, H., and Z. Voyer, D., Filsfils, C., Parekh, R., Bidgoli, H., and Z.
Zhang, "Segment Routing Point-to-Multipoint Policy", Zhang, "Segment Routing Point-to-Multipoint Policy",
draft-voyer-pim-sr-p2mp-policy-02 (work in progress), July draft-ietf-pim-sr-p2mp-policy-00 (work in progress), July
2020. 2020.
[RFC6513] Rosen, E., Ed. and R. Aggarwal, Ed., "Multicast in MPLS/ [RFC6513] Rosen, E., Ed. and R. Aggarwal, Ed., "Multicast in MPLS/
BGP IP VPNs", RFC 6513, DOI 10.17487/RFC6513, February BGP IP VPNs", RFC 6513, DOI 10.17487/RFC6513, February
2012, <https://www.rfc-editor.org/info/rfc6513>. 2012, <https://www.rfc-editor.org/info/rfc6513>.
[RFC7432] Sajassi, A., Ed., Aggarwal, R., Bitar, N., Isaac, A., [RFC7432] Sajassi, A., Ed., Aggarwal, R., Bitar, N., Isaac, A.,
Uttaro, J., Drake, J., and W. Henderickx, "BGP MPLS-Based Uttaro, J., Drake, J., and W. Henderickx, "BGP MPLS-Based
Ethernet VPN", RFC 7432, DOI 10.17487/RFC7432, February Ethernet VPN", RFC 7432, DOI 10.17487/RFC7432, February
2015, <https://www.rfc-editor.org/info/rfc7432>. 2015, <https://www.rfc-editor.org/info/rfc7432>.
[RFC7988] Rosen, E., Ed., Subramanian, K., and Z. Zhang, "Ingress [RFC7988] Rosen, E., Ed., Subramanian, K., and Z. Zhang, "Ingress
Replication Tunnels in Multicast VPN", RFC 7988, Replication Tunnels in Multicast VPN", RFC 7988,
DOI 10.17487/RFC7988, October 2016, DOI 10.17487/RFC7988, October 2016,
<https://www.rfc-editor.org/info/rfc7988>. <https://www.rfc-editor.org/info/rfc7988>.
Appendix A. Illustration of a Replication Segment Appendix A. Illustration of a Replication Segment
This section illustrates an example of a single Replication Segment. This section illustrates an example of a single Replication Segment.
Examples showing Replication Segment stitched together to form P2MP Examples showing Replication Segment stitched together to form P2MP
tree (based on SR P2MP policy) are in [I-D.voyer-pim-sr-p2mp-policy]. tree (based on SR P2MP policy) are in [I-D.ietf-pim-sr-p2mp-policy].
Consider the following topology: Consider the following topology:
R3------R6 R3------R6
/ \ / \
R1----R2----R5-----R7 R1----R2----R5-----R7
\ / \ /
+--R4---+ +--R4---+
Figure 1 Figure 1
A.1. SR-MPLS
In this example, the Node-SID of a node Rn is N-SIDn and Adjacency- In this example, the Node-SID of a node Rn is N-SIDn and Adjacency-
SID from node Rm to node Rn is A-SIDmn. Interface between Rm and Rn SID from node Rm to node Rn is A-SIDmn. Interface between Rm and Rn
is Lmn. is Lmn.
Assume a Replication Segment identified with R-ID at replication node Assume a Replication Segment identified with R-ID at replication node
R1 and downstream Nodes R2, R6 and R7. The Replication SID at node n R1 and downstream Nodes R2, R6 and R7. The Replication SID at node n
is R-SIDn. A packet replicated from R1 to R7 has to traverse R4. is R-SIDn. A packet replicated from R1 to R7 has to traverse R4.
The Replication Segment state at nodes R1, R2, R6 and R7 is shown The Replication Segment state at nodes R1, R2, R6 and R7 is shown
below. Note nodes R3, R4 and R5 do not have state for the below. Note nodes R3, R4 and R5 do not have state for the
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Replication Segment <R-ID,R1>: Replication Segment <R-ID,R1>:
Replication SID: R-SID1 Replication SID: R-SID1
Replication State: Replication State:
R2: <R-SID2->L12> R2: <R-SID2->L12>
R6: <N-SID6, R-SID6> R6: <N-SID6, R-SID6>
R7: <N-SID4, A-SID47, R-SID7> R7: <N-SID4, A-SID47, R-SID7>
Replication to R2 steers packet directly to R2 on interface L12. Replication to R2 steers packet directly to R2 on interface L12.
Replication to R6, using N-SID6, steers packet via IGP shortest path Replication to R6, using N-SID6, steers packet via IGP shortest path
to that node. Replication to R7 is steered via R4, using N-SID4 and to that node. Replication to R7 is steered via R4, using N-SID4 and
then adjacency SID A-sID47 to R7. then adjacency SID A-SID47 to R7.
Replication Segment at R2: Replication Segment at R2:
Replication Segment <R-ID,R2>: Replication Segment <R-ID,R2>:
Replication SID: R-SID2 Replication SID: R-SID2
Replication State: Replication State:
R2: <Leaf> R2: <Leaf>
Replication Segment at R6: Replication Segment at R6:
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o R1 performs PUSH operation with <N-SID4, A-SID47, R-SID7> label o R1 performs PUSH operation with <N-SID4, A-SID47, R-SID7> label
stack for the replicated copy to R7 and sends it to R2, the stack for the replicated copy to R7 and sends it to R2, the
nexthop on IGP shortest path to R4. R2 is the penultimate hop for nexthop on IGP shortest path to R4. R2 is the penultimate hop for
N-SID4; it performs penultimate hop popping, which corresponds to N-SID4; it performs penultimate hop popping, which corresponds to
the NEXT operation and the packet is then sent to R4 with the NEXT operation and the packet is then sent to R4 with
<A-SID47, R-SID1> in the label stack. R4 performs NEXT operation, <A-SID47, R-SID1> in the label stack. R4 performs NEXT operation,
pops A-SID47, and delivers packet to R7 with <R-SID7> in the label pops A-SID47, and delivers packet to R7 with <R-SID7> in the label
stack. R7, as Leaf, performs NEXT operation, pops R-SID7 label stack. R7, as Leaf, performs NEXT operation, pops R-SID7 label
and delivers the payload. and delivers the payload.
A.2. SRv6
For SRv6 , we use SID allocation scheme, reproduced below, from
Illustrations for SRv6 Network Programming
[I-D.filsfils-spring-srv6-net-pgm-illustration]
2001:db8::/32 is an IPv6 block allocated by a RIR to the operator
2001:db8:0::/48 is dedicated to the internal address space
2001:db8:cccc::/48 is dedicated to the internal SRv6 SID space
We assume a location expressed in 64 bits and a function expressed
in 16 bits
Node k has a classic IPv6 loopback address 2001:db8::k/128 which
is advertised in the IGP
Node k has 2001:db8:cccc:k::/64 for its local SID space. Its SIDs
will be explicitly assigned from that block
Node k advertises 2001:db8:cccc:k::/64 in its IGP
Function :1:: (function 1, for short) represents the End function
with PSP support
Function :Cn:: (function Cn, for short) represents the End.X
function from to Node n
Each node k has:
An explicit SID instantiation 2001:db8:cccc:k:1::/128 bound to an
End function with additional support for PSP
An explicit SID instantiation 2001:db8:cccc:k:Cj::/128 bound to an
End.X function to neighbor J with additional support for PSP
An explicit SID instantiation 2001:db8:cccc:k:Fk::/128 bound to an
End.Replcate function
Assume a Replication Segment identified with R-ID at replication node
R1 and downstream Nodes R2, R6 and R7. The Replication SID at node
k, bound to an End.Replcate function, is 2001:db8:cccc:k:Fk::/128
with ARG value 0. A packet replicated from R1 to R7 has to traverse
R4.
The Replication Segment state at nodes R1, R2, R6 and R7 is shown
below. Note nodes R3, R4 and R5 do not have state for the
Replication Segment.
Replication Segment at R1:
Replication Segment <R-ID,R1>:
Replication SID: 2001:db8:cccc:1:F1::0
Replication State:
R2: <2001:db8:cccc:2:F2::0->L12>
R6: <2001:db8:cccc:6:F6::0>
R7: <2001:db8:cccc:4:C7::0, 2001:db8:cccc:7:F7::0>
Replication to R2 steers packet directly to R2 on interface L12.
Replication to R6, using 2001:db8:cccc:6:F6::0, steers packet via IGP
shortest path to that node. Replication to R7 is steered via R4,
using End.X SID 2001:db8:cccc:4:C7::0 at R4 to R7.
Replication Segment at R2:
Replication Segment <R-ID,R2>:
Replication SID: 2001:db8:cccc:2:F2::0
Replication State:
R2: <Leaf>
Replication Segment at R6:
Replication Segment <R-ID,R6>:
Replication SID: 2001:db8:cccc:6:F6::0
Replication State:
R6: <Leaf>
Replication Segment at R7:
Replication Segment <R-ID,R7>:
Replication SID: 2001:db8:cccc:7:F7::0
Replication State:
R7: <Leaf>
At R1, a H.Encaps.Replicate behavior is associated with the
replication segment. When a packet, (A,B2), is steered into the
replication segment at R1:
o Since R1 is directly connected to R2, R1 creates encapsulated
replicated copy (2001:db8::1, 2001:db8:cccc:2:F2::0) (A, B2), and
sends it to R2 on interface L12. R2, as Leaf, executes
decapsulation operation of End.Replicate, removes outer IPv6
header and delivers the payload.
o R1 creates encapsulated replicated copy (2001:db8::1,
2001:db8:cccc:6:F6::0) (A, B2) then forwards the resulting packet
on the shortest path to 2001:db8:cccc:6::/64. R2 and R3 forward
the packet using 2001:db8:cccc:6::/64. R6, as Leaf, executes
decapsulation operation of End.Replicate, removes outer IPv6
header and delivers the payload.
o R1 created encapsulated replicated copy (2001:db8::1,
2001:db8:cccc:4:C7::0) (2001:db8:cccc:7:F7::0; SL=1) (A, B2) and
sends it to R2, the nexthop on IGP shortest path to
2001:db8:cccc:4::/64. R2 forwards packet to R4 using
2001:db8:cccc:4::/64. R4 executes End.X function on
2001:db8:cccc:4:C7::0, performs PSP action, removes SRH and sends
resulting packet (2001:db8::1, 2001:db8:cccc:7:F7::0) (A, B2) to
R4. R7, as Leaf, executes decapsulation operation of
End.Replicate, removes outer IPv6 header and delivers the payload.
Authors' Addresses Authors' Addresses
Daniel Voyer (editor) Daniel Voyer (editor)
Bell Canada Bell Canada
Montreal Montreal
CA CA
Email: daniel.voyer@bell.ca Email: daniel.voyer@bell.ca
Clarence Filsfils Clarence Filsfils
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